A display device that includes display components including a liquid crystal panel includes a lighting unit behind the liquid crystal panel. The lighting unit may be an edge light type backlight that includes a light guide component closer to the liquid crystal panel and a light source closer to a side of the light guide component. In the edge light type backlight, light from the light source enters the light guide plate through an end surface, travels through the light guide plate, and exit the light guide plate through a surface on the front side. The light source may include light emitting diodes (LEDs). The light guide component is made of a material having higher light transmissivity, for example, a resin such as acrylic and polycarbonate. International Publication WO 2015/016091 discloses an edge light type backlight used for a display device.
The light source in the edge light type backlight is disposed slightly away from an end surface of the light guide component with a small gap. Because the light guide component is made of the resin such as acrylic and polycarbonate, the light guide component expands or contracts according to an ambient temperature or humidity. During light emission of the light source, heat is generated. If the light emission of the light source continues for long hours, the heat is transmitted to the light guide component and the light guide component expands. The end surface of the light guide component may contact the light source. If the light guide component contacts the light source, the light source may be broken and a portion may be illuminated. Furthermore, the resin of the light guide component may be burned due to the heat of the light source and the light transmissivity may decrease. As a result, uneven brightness (a dark sport) is less likely to occur.
As a screen size (a display area) of a display device increases, a size of a light guide plate increases. Therefore, an increase in size of the light guide component due to an expansion increases. The number of light source or an amount of light emission of the light source may be increased to increase an amount of light to illuminate the entire screen. In this case, an amount of heat from the light source increases and thus an amount of heat transmitted to the light guide component. As a result, the increase in size of the light guide component due to the expansion further increases.
In the lighting unit in WO 2015/016091, light guide plates are arranged at intervals. The light guide plates are configured to expand toward gaps between the light guide plates even if the light (guide plates expand due to the ambient temperature or humidity. Therefore, distances between the light source and the light guide plates are maintained constant and the light guide plates are less likely to contact the light source.
In the lighting unit in Patent Document 1, sizes of the gaps between the light guide plates and displacement of the light guide plates in a thickness direction, a loss occurs in amount of entering light transmitted from the light guide plate to the light guide plate and thus light use efficiency decreases. Furthermore, the sized of the gaps between the light guide plates vary due to the expansion and the contraction of the light guide plates according to the ambient temperature or humidity. Therefore, a variation in the light use efficiency according to the ambient temperature may cause uneven brightness. Still furthermore, the gaps between the light guide plates are located in the display area of the liquid crystal panel, a difference between an amount of light that leaks through the gaps between the light guide plates and an amount of light that exits through the planar surfaces of the light guide plates may cause uneven brightness.